Agent Brian Terry Shot in Back with AK-47 During Gunfight, Family Says

A member of an elite U.S. Border Patrol tactical team was shot and killed Tuesday night reportedly during a violent gun battle in a remote Arizona canyon just north of the U.S. border with Mexico, authorities said Wednesday.

Agent Brian Terry, 40, was in pursuit of bandits who prey on illegal immigrants and drug smugglers as they try to enter the U.S. when his team encountered a group of suspects, some of whom opened fire.

"They said he shot one of them, and then one came up behind him and shot him in the back with an AK-47," the agent's stepmother Carolyn Terry told ABC News, relating what she was told by U.S. Customs and Border Protection officials.

"Brian was still able to call for assistance, and the helicopter was there within minutes and they life-flighted him," she said. "The chaplain told me he died en route, but we don't know."

National Border Patrol Council President T.J. Bonner said Terry encountered the bandits with three other agents when the gunfight began.

"We can't believe it," said an emotional Terry. "He was coming back for Christmas on Friday. He had his ticket bought and everything."

Officials have detained four suspects in conjunction with the shooting and are still pursuing a fifth, CBP said in a statement. Border Patrol agents and local law enforcement officers have been fanning out across the area with K9 teams to track down the suspect.

"Our thoughts and prayers are with the Terry family for their tragic loss," said CBP Commissioner Alan Bersin. "Our commitment to Agent Terry and his family is that we will do everything possible to bring to justice those responsible for this despicable act."

The incident occurred in an area known as Peck Canyon by Rio Rico, Ariz., which is north of Nogales and south of Tucson, along Interstate 19.

The corridor is known as a funnel for illicit flows of immigrants, drugs and weapons. And as border security has tightened, officials say, the area has become more dangerous and rife with bandits.

"These are just common thugs, they really have no sense of morals," Bonner said of the bandits. "Illegal aliens who are coming across are carrying their life savings with them...and so these bandits are well aware of that and they take advantage of that."

Gary Gay, former mayor of Patagonia, Ariz., said that the rugged, dark canyon area has provided cover for the bandits to act. "Sometimes they even steal the dope right off the mules before they can get it up to Tucson," he said.

Slain Border Agent Praised as "Tough Guy"

The FBI and Santa Cruz County Sheriff's Office are leading the investigation into Terry's death.

The Arizona National Guard, which presently has 560 troops dispersed along the border to support the Border Patrol, said its members were not involved with the incident.

Carolyn Terry, who lives in Jonesville, Michigan, where Brian grew up, praised her stepson as a "tough, big guy" who dedicated his life to public service.

Brian joined the Marines right out of high school and served three years, including a tour of duty in Iraq. He was honorably discharged in 1994 and later became a local police officer. Terry joined the Border Patrol in 2007.

For the past year, he was a member of the patrol's elite operations team known as BORTAC, for Border Patrol Tactical Unit .

"He loved his job," she said. "He used to call us when he was going out on a mission and call again when he got back in. He loved the excitement."

Terry's murder is the first death of a Border Patrol agent in the line of duty since July 2009, when Agent Robert Rosas was killed on patrol along the border in southern California.

The Terry family said Brian's body is being flown home to Michigan, where it will hold memorial services in the next few days.